Atomically dispersed metal-nitrogen-carbon electrocatalysts for oxygen reduction reaction: from synthesis strategies to activity engineering

Atomically dispersed catalysts show great potential in many energy and catalysis fields due to their maximum atom utilization efficiency, tunable electronic structures, and favorable catalytic performance. In particular, atomically dispersed metal nitrogen-carbon (M-N-C) catalysts deliver outstanding activity and selectivity for the oxygen reduction reaction (ORR). At present, although considerable efforts have been made in this field, the precise regulation of well-defined active structure and the effective improvement of catalytic activity remain two major challenges in the development of highly efficient M-N-C catalysts at the atomic scale. Herein, the effective synthesis strategies for realizing well-defined active dispersion are systematically summarized, which is expected to provide valuable guidance for further study. Then, activity engineering to atomically dispersed M-N-C including improvement of intrinsic activity and active sites density are discussed in detail with an aim to clarify structure-property correlations. Finally, the existing problems and prospects regarding the development of atomically dispersed M-N-C catalysts for ORR are proposed.